U.S. Pat. No. 4,879,170 describes a nonwoven elastomeric web formed by hydraulically entangling a nonwoven meltblown web with pulp fibers, staple fibers, additional meltblown fibers or continuous filaments, at least one of which fibers is elastomeric. Elastomeric materials described as suitable for forming an elastomeric meltblown web include polyesters, polyurethanes, polyetheresters and polyamides referring to U.S. Pat. No. 4,657,802. Other elastomeric materials are mentioned, however, not in reference to formation of meltblown fibers. Such elastomers include elastomeric polyolefins, elastomeric copolyesters and ethylene/vinyl acetates. The co-formed material is described as being a smooth elastic with good hand, drape and other properties.
U.S. Pat. No. 4,724,184 describes an elastomeric nonwoven web formed by meltblown fibers comprised of a polyether/polyamide block copolymer such as sold under the trade designation PEBAX.TM. 3533. The elastic meltblown nonwoven web formed from this elastomer is a coherent matrix of microfibers with optionally secondary fibers incorporated into the web.
Additional patents describing elastomeric meltblown webs include U.S. Pat. No. 4,663,220 which describes polyalkenyl arenes/polydiene block copolymers such as A-B-A block copolymers sold under the trade designation KRATON.TM. G, which include polystyrene/polyethylene-butylene/polystyrene block copolymers. These block copolymers are blended with polyolefins to enhance processability into formation of the elastomeric meltblown web, which elastomeric webs are also discussed in U.S. Pat. No. 4,789,699.
U.S. Pat. No. 4,741,949 describes an elastomeric web formed from a polyether/polyester. Again, the web may optionally contain secondary fibers distributed therein including wood pulp, staple fibers, super-absorbent fibers or binding fibers. The loading of the secondary fibers depends on the fiber average length, with smaller fibers, less than 0.5 in. in length, includable up to 80 weight percent of the web, whereas larger fibers are only includable up to 40 weight percent.
U.S. Pat. No. 4,908,263, to Reed et al., describes a nonwoven insulating fabric formed from elastomeric meltblown fibers admixed with staple bulking fibers. The bulking fibers having on average at least 1/2 crimp/cm. The meltblown materials described are formed from elastomeric polyurethanes, polyesters, polyamides or polyalkenyl arene/polydiene block copolymers such as polystyrene/polydiene block copolymers. The preferred elastomeric material is a polyurethane.
There continues to be a need for elastomeric meltblown webs for a variety of applications specifically formed from thermoplastic polymers having improved meltblown processing characteristics and useful elastic and tensile properties in a meltblown web form.